With prelinking disabled (see bug #10518), there are still some differences between builds because of non-reproducible image creation, for example in /etc/passwd and /etc/group (order of entries is different). Probably needs to be solved as part of core image building (Sorting the files after package install? Special adduser/addgroup which ensures sorting?). This issue here is about checking that a full distro (like Ostro) has no unexpected changes during an update.
See "[PATCH 1/1] rootfs-postcommands.bbclass: sort passwd entries". I've not found other reasons for unnecessary changes during updates, so if that gets merged, I consider this issue resolved (for now...).